Device for supercritical water oxidation of materials

ABSTRACT

A method and device for oxidization of materials in supercritical water. The method involves a) introducing a fluid containing water and an oxidizing agent in a ring-shaped area and through a first end of a substantially tube-shaped reactor comprising an external wall and an internal tube, b) heating the fluid in the ring-shaped area, c) introducing the heated fluid into the internal tube and simultaneously introducing material to be treated into said internal tube at a second end of the reactor, d) mixing the fluid and the material to be treated in a first portion of the internal tube, followed by cooling the obtained mixture in a second portion of the internal tube, and e) isobarically discharging the fluid/oxidized material from the internal tube of the reactor.

TECHNICAL FIELD

The present invention relates to a process for supercritical wateroxidation of materials as well as to a device that can be used forimplementing this process. The present invention also provides a processfor treating wastes.

In the context of the invention material is defined as any substance orcomposition capable of being subjected to a hydrothermal oxidationprocess.

The applications of this process can relate, for example, to thedestruction of materials such as toxic substances, organic compoundssuch as halogen solvents, or the treatment of materials such as highlytoxic or hazardous organic effluents such as, for example,. contaminatedwastes, explosives, as well as solvents, biological or pharmaceuticalcompounds, industrial slurries or effluents of the petroleum industry,etc.

Hydrothermal oxidation (HTO) is a recent technology for treating wastes.It is carried out by means of water at a temperature and pressure as thereaction medium for reacting an oxidant with the component(s) to bedegraded.

The oxidant can be in gas form—air, oxygen-enriched air, ozone,etc.—liquid oxygen, oxygen peroxide, etc.—when the oxidizing agent ismostly comprised of organic compounds in liquid form or in suspension inwater. It can also be pure or diluted in water at concentrations varyingfrom 20% by weight as described in Frisch, A. M. (1997), SupercriticalWater Oxidation. Standard Handbook of Hazardous Waste Treatment andDisposal, H. M. Freeman, McGraw-Hill, p.8.117-8.190.

The critical point of the water, Tc=374° C., Pc=221 bar allows twogroups to be defined in HTO processes:

When one of the two operational conditions of the oxidation reaction issituated below the critical point of the water, such methods are alsoknown as wet oxidation procedure (WOP), the oxidation reaction takingplace in the aqueous phase, and

when the two operating conditions of the oxidation reaction are situatedabove the critical point, one speaks of supercritical thermal oxidation(WTO), because the reaction takes place in the supercritical water in ahomogeneous phase where all of the reactants are solubized out of thesalts, whose solubility products reduce consequent to the reduction ofthe electrical permittivity of the water with the increase of thepressure or temperature.

The WTO process differs from the WOP process principally by the factthat the reaction is much more rapid, the characteristic time are of theorder of a minute instead of tens of minutes, and is often morecomplete, the rates of destruction systematically exceeding 99.99%instead of the 98% for WOP. On the other hand, WOP is less sensitivethan WTO to the heteroatom content of the organic matrix of the wastesto be treated.

Because of the positioning of the WOP processes in low pressures and lowtemperatures ; in other words, below the critical point, they do notenter into a competition with the supercritical processes.

PRIOR ART

In the early 80's the potentialities for destruction of organic wastesin supercritical water were established and numerous modifications weremade thereafter in order to make possible treatment of more increasinglymore diverse organic wastes. However, exploitation on the industrialscale still needed to be optimized.

Supercritical oxidation method is currently implemented in a rudimentaryreaction zone comprised of a simple reactor. This technological solutionhas the advantage of being easy to construct as well as to use. Inaddition, its investment and maintenance costs are relatively low.

However, the composition of the wastes that can be destroyed in thistype of reactor is rather limited by reason of the deposition of mineralcompounds that create a blockage or due to the corrosion induced by thepresence of halogen compounds. In fact, the presence of mineral slats atconcentrations of the order of 1% in a supercritical water reactorgenerates precipitates that deposit on the walls of the reactor. Inaddition, when the waste contains more than several milligrams ofchlorine, the stainless steel or the nickel-based materials undergo acorrosion to the redhibitory requirements in industrial exploitation.

None of the developments have responded to the requirements fortreatment of wastes containing corrosive compounds or mineral salts.

The objectives of the specialists in this method are as follows:

to obtain consistently elevated rates of destruction while reducing tothe extent possible the passage time and reaction temperature,

resistance to corrosion, and

limiting the precipitation of the mineral salts.

It is therefore necessary to develop new devices in order to resolvethese problems of rapid corrosion or accumulation of salts as describedin Schmieder, H. and Abeln, J (1999). SCWO: Facts and Hopes. GVCSpecialist Committee “High Pressure Chemical Engineering” Karlsruhe, pp.81-86.

In addition, when it concerns adding a third compound, for example forincreasing the solubility of a new chemical species, the currentsolutions are not applicable but to a very precise organic compound andthus cannot be extended to a mixture of wastes.

SUMMARY OF THE INVENTION

The present invention has specifically the object of providing a processfor treating a material by hydrothermal oxidation that does not have theafore said drawbacks and which responds to the aforesaid objectives.

The method of the present invention comprises the following steps:

a) introducing a fluid comprising water and an oxidizer under a pressureabove 22.1 MPa into an annular zone and at one end of an essentiallytubular reactor comprising an outer wall and an inner tube, the annularzone of the reactor being defined by the outer wall and the inner tube;

b) heating the water/oxidizer fluid in said annular zone to atemperature above 374° C.;

c) introducing the heated and pressurized water/oxidizer fluid obtainedin step b) into the inner tube of the reactor at a second end of thereactor and simultaneous introduction of the material to be treated intosaid inner tube at said second end of the reactor;

d) mixing the heated and pressurized water/oxidizer fluid and thematerial to be treated into a first part of said inner tube in such afashion as to oxidize the material to be treated, followed by cooling ofthe fluid/oxidized material mixture into a second part of the innertube, and

e) isobaric evacuation of the cooled fluid/oxidized material mixturefrom the reactor directly from the inner tube to the first end of thereactor,

the fluid and the material continuously or quasi-continuously runningthrough the inner tube.

The material can be, for example, one of those cited in the presentdescription, for example, the majority of the organic compoundsoxidizable in supercritical water, for example aliphatic solvents suchas hexane, dodecane, etc., the aromatic solvents such as benzene,phenol, toluene, pyridine, etc., the halogen solvents such aschloroform, dichloromethane, trichloroethane, etc.

The method can also be used for destroying a material such as toxic orhazardous organic compounds such as those comprising effluentscontaminated with radio-elements generated by the nuclear industry, usedoils, ion exchange resins, etc., chemical arms or explosives, as well aspharmaceutical compounds.

According to the invention, the material can be, for example, in theform of a waste for treatment, for example, liquid or in suspension.

Also, the present invention similarly provides a method for treatment ofa waste by hydrothermal oxidation comprising especially a stagecomprising the utilization of a process for treating a material byhydrothermal oxidation according to the invention, the material beingthe waste.

According to the invention, the oxidizer can be, for example, a gaschosen from the group comprising ozone and an oxygen-nitrogen mixture,or a liquid chosen from the group comprising hydrogen peroxide andliquid oxygen.

According to the invention, the oxidizer is preferably introduced withthe water into the reactor in a quantity in the range of 1 to 5 timesthe stoichiometric quantity necessary to oxidize the material. Thisquantity can be determined specifically using the quantity of materialto be treated, for example waste to be destroyed.

For example, in the case of a waste to be treated, it can be mixed withthe fluid either pure or diluted in water, for example at a mass percentin the range of 10 and 100% or added from a third body present in orderto facilitate the oxidation reaction or favoring precipitation ofcertain mineral salts. The third body can be, for example, soda, sodiumnitrate, and nitric acid.

In step d) of the method of the invention, the mixture can be producedby agitation the reaction medium formed by the mixture of thesupercritical/material to be treated. The agitation allows on the onehand assuring a satisfactory temperature transfer between the flux andthe heating and cooling zones and on the other hand avoidingsedimentation or accumulation of the mineral salts that can precipitatein the course of the procedure. It thus permits assuring that a minimalvolume is employed in order to obtain destruction yields obtained insupercritical thermal water oxidation in standard configurations.

According to the invention, the heated mixing of the pressurizedwater/oxidizer fluid and of the material to be treated in the inner tubecan be produced, for example, by means of an agitation operating in astate equivalent to that of a perfectly-agitated reactor or in a statewhich tends towards that of a perfectly agitated reactor. According tothe invention, the pressurized heated water/oxidizer fluid mixture adthe material to be treated in the inner tube can be produced, forexample, using agitation, which confines' the agitation to successivevolumes in such a fashion as to obtain an essentially quasi-piston flowregime inside the inner tube of the pressurized heated water/oxidizermixture and the treated material.

According to the invention, oxidation of the material of step d)releases heat, which can be used to heat by counter-current thewater/oxidizer fluid at step b). Thus, according to the invention, thesupercritical fluid can be heated in the annular zone, for examplebetween 374° C. and 600° C., on the one hand by the supercriticalfluid/waste mixture passing in counter-current in the inner tube and onthe other hand by a means of heating or heating zone such as that of thedevice according to the present invention.

According to the invention, in step e), cooling of the fluid/oxidizedmaterial mixture in the inner tube is preferably obtained under strongagitation.

The present invention also provides a device that can be used forimplementing the method of the invention that utilizes a supercriticalmedium. This device comprises

a main body comprised of a substantially tubular wall equipped at afirst end with a flange, sealing means, a first inlet for the componentsof the supercritical mixture and an evacuation outlet for the treatedmaterial., the flange being eventually equipped with a tight passage forreceiving a rotary shaft and a second of its ends having a second inletfor introducing the material to be treated into the device, the mainbody, the flange and the sealing means being made of materials resistantto the pressures of the supercritical media

an inner tube disposed on the inside of the main body in such a fashionas to form an annular zone along said main body, the inner tubecomprising a opening, a first end and a second end, the first end beingfixed with the flange in such a fashion that the opening of the innertube is isolated and in such a fashion tight with respect to the annularzone in communication at once with the treated material outlet and withthe passage, the second end of the inner tube being at the second end ofthe main body in such a fashion that the opening is at this level incommunication with the annular zone and with the second material inletsuch that the material to be treated can be introduced at this point andnot into the annular zone but directly into the lumen of the inner tube;

a agitation means disposed in the lumen of the inner tube and operatedby means of a rotating shaft;

a refrigeration means disposed around the main body and over a firstpart of same in such a fashion as to cool the treated material situatedinside the tube prior to its evacuation from the device through thetreated material outlet, and

heating means disposed around the main body and over a second part ofsame in such a fashion as to heat the components of the supercriticalmedium in order to form the supercritical medium prior to its entry intothe inner tube at its second end.

The inner tube 19 is preferably placed at a distance from the secondentry of the main body thus assuring prevention of reflux of thematerial or of its degradation products towards the end of the innertube, thus protecting the main body from any contact with the materialin the supercritical medium.

According to the invention, the inlet for the components of thesupercritical medium can be created by piercing the flange.

According to the invention the device can comprise in addition a metalfitting disposed in all or part of the annular zone. Said fitting allowsincreasing the turbulence of the fluid flow within said zone, assuringan enhanced thermal transfer, and making possible the thermal transferby conduction between the inner tube 19 and the main body.

According to the invention, the device can comprise in addition aninjector making possible introduction of the material to be treateddirectly into the inner tube at the second inlet, preferably at adistance consistent with the end 27 of the inner tube in order toprevent the reflux of the material into the supercritical medium. Theinjector can be, for example, a tube with a diameter less than that ofthe inner tube.

According to the invention, another refrigeration means can be placedaround the main body at the end where the material is injected.

According to the invention, the agitation means can comprise rotaryelements chosen from a helix, a turbine, a flat blade, and an anchor.For example, in the case of utilization of blades, as a function of thegeometry of the blades, the agitation effect can either tend in thedirection of an operation equivalent to a perfectly agitated reactor or,if intercalaries are installed on the blades, agitation can be confinedto successive volumes in order to conserve a quasi-piston flow regime.For example, in the case of helices, their number can vary and be chosenparticularly as a function of the turbulence to be imposed on thesystem.

According to the invention, the rotating shaft can be associated with adrive motor coupled to a frequency variatot allowing rotational speedsto be obtained in the range of 0 to 1,500 rpm.

According to the invention, the main body and the flange can be, forexample, made of stainless steel or nickel-based or in any knownmaterial having the aforementioned required properties.

According to the invention, the seal means can comprise means making itpossible to assure a tight connection between the main body and theflange, preferably up to 35×10⁵ Pa and temperatures running, forexample, from 20 to 250° C. Said seal means can be, for example, a typeof joint either metallic, for example flat or helicoflex (registeredtrademark), or a high strength polymer. The connections known to thespecialist in the art for this application can be utilized.

According to the invention, the seal means can comprise seal means atthe passage in order to receive the rotating shaft. The temperature ofthe fluid at the level of said seal does not, in principle, exceed 250°C. and it is, for example, a rotating connection of the high pressuresealed joint for a rotary shaft. The joints know to the specialist inthe art for this application can be used. A magnetic coupling of thestandard type installed in the flange can also be used.

According to the invention, the materials comprising the injector, theinner tube, the agitation means can be chosen to be identical ordifferent in virtue of their capacity to resist chemical attack. It isnot necessary that they have a good hold under pressure. It is furthernot essential that these parts be made of the same material. Said lattercan be chosen, for example, as a function of the chemical nature of thewaste to be destroyed. For example, it can be chosen from the groupcomprising a stainless steel, a heat and oxidation resistant nickelalloy of the [Ni58, Fe20 Mo20] type, titanium, and ceramic. It may be,for example, an Iconel (trademark) or a Hastelloy (trademark).

In a device according to the present invention, all of these parts aresubject to any significant mechanical stress. Preferably they havesatisfactory behavior relative to temperature, especially up to 600° C.and to corrosion. These parts are also easily changeably and can beconsidered, under certain circumstances, as expendables.

According to the invention, the inner tube can, for example, have athickness of approximately 1 mm.

When coupling, according to the present invention, the inner tube to theagitation system, the device has a number of operational advantageswhich are disclosed in the following.

The envelope forming the inner tube is in equipressure; in other words,it is not used in order to assure containment at the high pressures ofthe reactor. It is thus possible to use different materials having agood resistance to corrosion but a lesser resistance to mechanicalstresses. In the case, wherein the thermal exchanged must be made overthe small dimension surfaces, the materials that have good thermalconductivity are preferred, for example, titanium, noble metals, etc.,with regard to the materials known for their very good chemicalresistance but poor conductors such as ceramic.

Although the use of materials having better resistance to pressureprolongs the service life of the reactor as compared with corrosion, thestandard inner tubular envelope is easy to access and its replacementinvolves little labor and low cost.

In addition, the internal elements of the device or reactor that are indirect contact with the waste of which are not subjected to the stressof high pressures and can be made of materials resistant to corrosion oreasily renewable.

The device of the present invention thus allows carrying out anoxidation reaction in supercritical water by means of reactor having aninner envelope and an agitator in the reaction and refrigeration zones.

It makes possible having one of the ends of the reactor cold by imposingin the direction of circulation a counter-current from one end to theother of the wall. This involves that the agitation system used requireonly assuring a seal at high pressure with temperatures below 250° C.and not at the supercritical conditions of the water (P_(c)>221 bar andT_(c)>374° C.).

According to the invention, the refrigeration means placed around themain body can be, for example, a double-envelope refrigerant.

According to the invention, the heating means disposed around the mainbody can be, for example, in the form of a sleeve. It can, for example,be a cuff heater band. This type of cuff is known to the specialist inthe art.

According to the invention, the total length of the device and theinternal diameter of the main body depend on:

integration of the inner tube or reaction tube and, possibly of theparts necessary for its alignment with the main body;

on mechanical requirements, for example, P_(max)=350 bar.

on thermal requirements : for example, the second end of the main bodycan be 600° C., while the first extremity, at the level of the flangewith the seal, at 250° C.;

integration and agitation in the inner tube;

on the holding time of the waste with the oxidizer in the hot zone, forexample at a temperature T>400° C., comprised for example between 10 sand 5 minutes.

on the holding time of the oxidized flux in a refrigeration zonesufficiently long in the inner tube to assure an exit temperature of thetreated waste between 20 and 250° C.

According to the invention, the reactor has preferably a longitudinalform whose greater dimension corresponds to the axis of agitation.

The present invention provides, as a result, a reaction zone ofhydrothermal oxidation allowing, in particular:

carrying out of the oxidation reaction between the material, for examplea waste, and the oxidizer in the supercritical water medium; in otherwords, T>374° C. and P>22.1 MPa;

grouping the reaction zone and the cooling zone and assuring a stronglyturbulent flow for better efficiency of thermal transfer and reactionkinetics, as well as preventing sedimentation of the precipitated metalsalts before, during and after oxidation of the material;

using an simple inner tube or envelope without the requirement ofpressure that is in contact with the initial material, for example thewaste, and the oxidized fluid in the high temperature zones. Said innertube or envelope can be interchangeable in order to either adapt to theconstruction material to the nature of the material to be treated, forexample to the waste to be eliminated, or to utilize a less onerousmaterial in order to carry out maintenance of the corroded parts;

implement an agitation means for the reaction zone situated in the innertube that is standard and simple to install;

The technical means provided by the present invention are, inparticular:

the definition of a pressurized compartment, whose tight joints of thelarge diameter openings are at temperatures lower than 250° C.;

utilization of an internal tube not subjected to the pressurerequirements in the main body, which can be called an autoclave, underpressure, for confining the organic compounds and the oxidationreactions to a zone resistant to or allowing corrosion and not having toassure the hold in pressure constituted by the lumen of the inner tube;

the opportunity to utilize a standard high-pressure magnetic coupling ina low temperature zone for operating the agitator blades in the zones inthe temperature range of 20 to 600° C.

The supercritical water oxidation reactor of the present invention isdistinguished especially from those of the prior art by theimplementation of an agitation system in the inner envelope inequipressure.

According to the present invention, the agitation has the role, inparticular, of assuring an especially turbulent operation, so as to:

facilitate the thermal transfers for heating the fluids prior to entryinto the reaction zone but also for cooling the fluids and treatedmaterials after oxidation;

assure a very satisfactory temperature homogeneity and of the reactionmixture composition over the radial axis of the reactor;

guarantee the short holding time in order to obtain optimal rates ofdestruction and thus to operate with a lower volume under pressure andtemperature than that of the prior art;

maintain in suspension all of the particles either that are contained inthe initial waste or that form after oxidation of the organic matrix ofthe waste. By avoiding sedimentation of the mineral salts in thereaction zone and in the cooling zone, in particular at passage of thecritical point, formation of a blockage no longer occurs as opposed tothe prior art, and it is thus possible to operate over longer periodswith wastes, whose content in mineral compounds is, for example, between0 and 20%.

Other features and advantages will become obvious when reading theexamples that are provided illustratively and non-limitingly hereinbelowwith reference to the attached figure.

FIGURE

FIG. 1 is a diagram of one embodiment of the device according to theinvention.

EXAMPLES

Device

FIG. 1 is a diagram of one embodiment of the device according to thepresent invention. It represents in particular a reaction zone accordingto the present invention.

In this embodiment, the device 1 comprises a main body 3 having asubstantially tubular form and equipped at the first of its ends with aflange 5, sealing means 7, a first inlet 9 for the components of thesupercritical medium, and an evacuation outlet 11 for the treatedmaterial. The flange 5 is equipped with a sealed passage 13 forreceiving the rotating shaft 15.

The second end of the main body 3 is provided with a second inlet 17 forintroducing the material to be treated into the device. The main body,the flange and the sealing means are made of materials resistant to thepressures and temperatures of the supercritical medium.

An inner tube 19 is disposed on the inside of the main body 3. It formsan annular zone 21 along the length of said main body. Said inner tubecomprises a lumen 23, a first end 25 and a second end 27. The first end25 is fixed to the flange 5 in such a fashion that the lumen 23 of theinner tube 19 is, isolated and sealed with regard to the annular zone21, in communication at once with the treated material outlet 1 and withthe passage 13. The second end 27 of the inner tube is at the second endof the main body 3 in such a fashion that the lumen 23 is at this pointin communication with the annular zone 21 and with the second inlet 17.Thus, the material to be treated can be introduced, at this point, notinto the annular zone 21 but directly into the lumen 23 of the innertube 19.

An agitation means 29 comprised of a rotating shaft 15 operating it andthe rotary elements 37 is place in the lumen 23 of the inner tube 19. Arotary joint of the high pressure type sealing joint for a rotary shaft(not shown) is placed at the level of the passage 13 for receiving therotating shaft 15.

A refrigeration means 31 is placed around the main body and over a firstpart of same in such a fashion as to cool the treated material situatedin the inner tube 19 prior to its evacuation from the device 1 throughthe treated material outlet 11.

Another refrigeration means 32 can also be placed over the second end ofthe main body.

A heating means 33 is placed around the main body and over a second partof same in such a fashion as to heat the constituents of thesupercritical medium in order to form the supercritical medium before itenters into the inner tube 19 at the level of the second end 27.

The outer part of the main body 3 of the device of the presentinvention, whose function it is namely to maintain a pressure in therange of 220 and 350 bar and to assure satisfactory heat transferbetween the inner reaction zone and the exchangers, will be describednow and then the internal elements will be described.

The Main Body or Autoclave

The main body 3 is made of stainless steel. The same applies to theflange 5. The sealing means 7, or joint, between the body and the flangeis a helicoflex (registered trademark) metal joint or another jointhaving an endurance for a temperature>250° C.

The flange 5 is provided. with a spur or evacuation outlet 11 forevacuating the supercritical medium/treated waste mixture from the innertube 19 after the oxidation reaction and subsequent cooling. The spur orpassage does allows only the flow originating in the inside of thereaction tube 19. It is sufficiently wide to facilitate circulation of afluid containing material in suspension.

A metal fitting (not shown) in the form of stainless steel balls can beplaced in the annular zone. The use of such a fitting is explainedabove.

A frequency variator is coupled to the agitator motor making it possibleto obtain rotational speeds of the blades between 0 and 1,500 rpm.

The Reaction Tube

The inner reaction tube 19 is the seat of the supercritical wateroxidation reaction.

Its wall is of a thickness of approximately 1 mm, its inner and outersurfaces are in equipressure. An agitator is arranged on the inside andcomprises a central shaft 15 and blades 37.

The temperature on the inside of the tube 19 can reach to 600° C. in thezone where the organic compounds of the wastes are oxidized. Thistemperature is then lowered to between 20 and 250° C. in the part in theproximity of the refrigerating envelope 31.

The Method

The water and the oxidizer are introduced cold under pressure throughthe port 9 into the annular zone 21 between the inner tube 19 and thehigh pressure wall comprising the main body 3, in order to form adiphasic mixture. This diphasic mixture transfers part of its caloriesoriginating from the hot flux comprised of the fluid water/waste mixturepresent in the inner tube towards the refrigerated double envelope wherea refrigerated fluid circulates.

The fluid; that is, the mixture of water and oxidizer, circulatesinitially in the annular zone 21 between the main body 3, forming thechamber of the device, and the inner tube 19. This zone or annular space21 is the seat of a heat transfer between the fluid at the inside of theinner tube 19 and the refrigeration means or cooler 31.

At all times in the annular zone 21, the water+oxidizer fluid is thenbrought to 400° C. by an external exchanger or heating means 33. Thewater+oxidizer product is pre-heated in addition by a part of thecalories originating from the fluid circulating in the lumen of the tube19 by counter-current.

Having arrived at the second end of the main body or chamber, the hotfluid enters into the inner tube 19 at the same time as the waste. Theproportion of organic compounds comprising the waste in the water ispreferably between 1 and 15% by weight at the level of the inlet to theinner tube 19.

The supercritical fluid and the waste are mixed on the inside of theinner tube 19 and form the reaction mixture.

The waste, as well as the supercritical waste/fluid mixture, do not comeinto contact with the inner walls of the main body 3 because the wasteis introduced directly to the inside of the inner tube 19 by means ofthe injector 35 formed simply by means of a small tube of very smalldiameter.

The point of injection of the waste via the injector 35 is preferablysituated at a distance from the end 27 of the tube 19 greater than 5times at least of the inside diameter of the tube 19, so as to preventreflux of the material or its degradation products towards the end 27,thus protecting the body 3 from any contact with the material in thesupercritical medium.

The oxidation reaction takes place in the inner tube. It releases heatwhich is in part used for counter-current heating of the initialwater+oxidizer mixture situated in the annular zone 21.

The flow of the reaction mixture is then cooled in the inner tube 19 bybeing strongly agitated by the shaft 19 equipped with blades 37 in orderto assure good heat transfer. The blades 37 serve also to maintain insuspension the mineral salts that would have precipitated. The coldeffluent is then direction isobarically towards the outlet 11.

The inventors have oxidized in a first time dodecane in thesupercritical water at 450° C. and at 3×10⁵ Pa using the device and themethod disclosed hereinbefore.

Yields greater than 99.9% were obtained.

They then tested the operational conditions given in the following inTable 1 for treating the constituent elements of wastes indicated inTable 2 below.

TABLE 1 Operational Conditions Mass concentration of Nature the waste atthe of the inlet to the reaction Pressure Temperature Oxidant zone (%)221-350 380-650 O₂ 1-15 H₂O₂ O₂—N₂ mixes

TABLE 2 Compositions of Oxidizable Wastes Constituting Elements ofProportion of the the Wastes Constituents (%) Carbon, hydrogen, oxygen, 0-100 nitrogen Halogens (chlorine, 0-10 fluorine, phosphorous, etc.)Mineral salts 0-20

The yields obtained are the same as the aforesaid.

1-19. (canceled) 20: An oxidation device for the treatment of a materialin a supercritical medium comprising: a main body comprised of asubstantially tubular wall equipped at a first end with a flange, aseal, a first inlet for the components of the supercritical mixture andan evacuation outlet for the treated material, the flange beingeventually equipped with a tight passage for receiving a rotary shaftand a second of its ends having a second inlet for introducing thematerial to be treated into the device, the main body, the flange andthe seal being made of materials resistant to the pressures of thesupercritical media; an inner tube disposed on the inside of the mainbody in such a fashion as to form an annular zone along the length ofsaid main body, the inner tube comprising an opening or lumen, a firstend and a second end, the first end being fixed with the flange in sucha fashion that the lumen of the inner tube is isolated and in such afashion tight with respect to the annular zone in communication at oncewith the treated material outlet and with the passage, the second end ofthe inner tube being at the second end of the main body in such afashion that the lumen is at this level in communication with theannular zone and with the second material inlet such that the materialto be treated can be introduced at this point and not into the annularzone but directly into the lumen of the inner tube and without reflux ofsame to the annular zone; an agitator disposed in the lumen of the innertube and operated driven by means of a rotating shaft; a refrigerationdevice disposed around the main body and over a first part of same insuch a fashion as to cool the treated material situated inside the tubeprior to its evacuation from the device through the treated materialoutlet, and a heating device disposed around the main body and over asecond part of same in such a fashion as to heat the components of thesupercritical medium in order to form the supercritical medium prior toits entry into the inner tube at its second end. 21: The deviceaccording to claim 20, comprising in addition a metal fitting disposedin all or in part of the annular zone. 22: The device according to claim20, comprising in addition an injector for introduction of the materialto be treated directly into the inner tube from the second inlet. 23:The device according to claim 22, wherein the injector is a tube havinga diameter less than that of the inner tube. 24: The device according toclaim 20, wherein the inner tube has a thickness of approximately 1 mm.25: The device according to claim 20, wherein the rotating shaft isassociated with a drive motor coupled to a frequency variator enablingobtaining rotational speed of the blades in the range of 0 to 1,500rotations per minute.
 26. The device according to claim 20, wherein theagitator comprises rotating elements selected from the group consistingof a helix, a turbine, a flat blade and an anchor. 27: The deviceaccording to claim 20, wherein the injector, the inner tube and theagitator are made of an identical or a different heat and oxidationresistant material from the group consisting of a stainless steel, anickel alloy, a titanium, and a ceramic. 28: The device according toclaim 27, wherein the heat and oxidation resistant material is selectedfrom the group consisting of stainless steel, a nickel alloy, titanium,and a ceramic. 29: The device according to claim 28, wherein the nickelalloy comprises Ni58, Fe20, Mo20. 30: The device according to claim 20,wherein the refrigeration device placed around the main body is a doublerefrigerating envelope. 31: The device according to claim 20, whereinthe heating device placed around the main body is in the form of asleeve.